The present invention relates to separation of a magnetic medium or web from a substrate or paper by electrostatic means without adversely affecting information recorded on the magnetic medium or the paper.
In systems where respective segments of a magnetic tape are brought into contact with and are moved away from a sheet of paper by means of a movable member, there is a tendency for a segment of the tape to adhere to the paper for an undesirable length of time, often despite the method used to hold the paper in place. Generally, in xerographic recording systems, the substrate such as plain paper is held in place on a drum or flat bed by means of a constantly applied electrostatic force. In other image recording systems, the paper may be held in place by a vacuum or clamp means, the latter tending to impart a tension to the paper.
Thus, regardless of the method used to hold the substrate or paper in place, there is a distinct need to be able to effect separation of the tape segment from the paper a selected short period of time after contact of the tape segment with the paper and completion of transfer of images from the tape segment to the paper. This should be done without adversely affecting information recorded on the tape or the paper.
Accordingly, as reflected in the illustrated preferred embodiment of the present invention, an apparatus and method are provided for effecting said separation within a selected predetermined short period of time, without adversely affecting information recorded on the tape or paper. The apparatus comprises a movable member or platen constructed to form, together with the tape, a capacitive element, and a voltage source for providing a voltage drop across the capacitive element. The platen is disposed for moving the tape into contact with and away from the paper, the tape having an electrically-conductive layer and a magnetizable image layer disposed for engaging the paper, and the platen having an electrically conductive layer and an electrically insulative layer disposed for electrically insulating the conductive layers of the platen and tape from each other. The voltage source is coupled to provide a voltage drop across (difference of potential between) the conductive layers for a selected period of time. This causes an electrostatic force to exist between the conductors sufficient to overcome adherence of the tape to the paper, facilitating separation of tape from paper during the selected period of time as the platen is moved away from the paper. Separation is accomplished substantially independent of tape tension. This permits operation with significantly less tape tension which, in turn, preserves tape integrity and provides for reduced tape breakage and misregistration of tape with paper, more effective cleaning of the tape, and less wear of the tape and the tape cleaning devices.